confessions occur more readily with the polygraph than with a bogus pipeline—an interrogation accompanying the use of an inert machine that the examinee believes to be a polygraph. In the long run, evidence that a technique lacks validity will surely undercut its utility.

Polygraph Screening

Criterion of Truthfulness There are inherent difficulties in assessing the accuracy of polygraph testing in the screening situations of greatest concern to this study. Although the criterion of truthfulness is easy to establish in laboratory simulations, we have seen no indication of a clear and stable agreement on what criteria are used in practice for assessing the accuracy of security screening polygraph tests in any federal agency that uses the tests. In particular, there is inconsistency about whether the polygraph test is being judged on its ability to detect major security violations or on its ability to elicit admissions of security violations of any magnitude. Moreover, the federal agencies that use the polygraph for screening do not collect data in a form that allows data from the ongoing administration of polygraph programs to be used to assess polygraph accuracy.

Generalizing from Research Because the studies of acceptable quality all focus on specific incidents, generalization from them to uses for screening is not justified. For this reason, uncertainty about the accuracy of screening polygraphs is greater than for specific-incident polygraph testing.

Estimate of Accuracy Because actual screening applications involve considerably more ambiguity for the examinee and in determining truth than arises in specific-incident studies, polygraph accuracy for screening purposes is almost certainly lower than what can be achieved by specific-incident polygraph tests in the field. Accuracy can be expected to be lower because of two major differences between screening and specific-incident polygraph testing. First, because a screening examiner does not know what specific transgressions an examinee may be concealing, it is necessary to ask generic questions rather than specific ones. Such questions create considerably more ambiguity for examinees than specific questions, such that two examinees who have committed the same minor infraction might have very different interpretations of its relevance to a test question, and very different emotional and physiological reactions. Instructions to examinees may reduce, but will not eliminate such variations, which can only degrade the accuracy of a test. Second, the appropriate criteria for judging accuracy are different in the two situations. In the typical screening situation, it is difficult in principle to assess whether a negative answer is truthful, and therefore it is much harder to establish truth and estimate accuracy than



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